Matte surface films have a variety of useful purposes. Primarily, they form a good background for displaying printed or artful images on the film. The images can be printed onto the matte surface film by any conventional plastic printing process.
Mobil Chemical Company film product "70 MLT" is a matte surface biaxially oriented multilayer film. The base layer is oriented polypropylene and the matte surface skin layer comprises a mixture of polyethylenes and an ethylene-propylene-butene-1 terpolymer. The matte surface film has a dull surface appearance; that is, it is not shiny or glossy. Such a surface appearance is not typical of most biaxially oriented films used in packaging but is advantageous in that it provides an unusual appearance when reverse printed on the side opposite to the matte surface. The surface of such matte surface films is rough and can exhibit a high coefficient of friction which is undesirable in high speed film-forming machinery, or packaging printing equipment.
Machinability and processability of films is often related to the characteristics of the film surface which give it a low resistance to the relative motion of the film surface in contact with the film-forming machinery or packaging equipment. The matte surface texture can cause frictional resistance as the film is processed.
In U.S. Pat. No. 4,692,379, a film is described which has an upper heat sealable layer formed from an ethylene-propylene-containing copolymer or terpolymer and an antiblocking agent, the lower heat sealable layer is formed from an ethylene-propylene-containing copolymer or terpolymer and antiblocking agent and a quantity of silicone oil such that the coefficient of friction-reducing amount of the silicone oil will be present on an exposed surface of the upper heat sealable layer following mutual contact of the upper and lower surfaces. The silicone oil additive is described as having a viscosity of from about 350 to about 100,000 centistokes with about 10,000 to about 30,000 centistokes being preferred. An advantage of the invention as described in the '379 patent is that the silicone is present on the exposed surface of the lower layer in discrete microglobules which, to some extent, transfer to the upper surface upon contact. The silicone oil on the surfaces of the film facilitates machinability.
Japanese Patent Application Publication No. 2668799 describes a biaxially drawn multiple layer film characterized in that a surface layer of a composition comprised of components A and B are laminated on at least one surface of a biaxially drawn crystalline propylene polymer base layer. Component A is 100 parts by weight of at least one resin selected from a propylene-ethylene random copolymer of an ethylene content of 3 to 8 weight percent and a propylene-ethylene-butene-1 random copolymer of an ethylene content of 0.5 to 5 weight percent and a butene-1 content of 3 to 25 weight percent. Component B is 0.1 to 1.0 parts by weight of polydiorganosiloxane of a degree of polymerization n of 3500 to 8000. The film is said to have markedly improved adaptability to packaging machines and suitability for high speed automatic packaging equipment.
U.S. Pat. Nos. 4,487,871 and 4,508,786 disclose a polyolefin resin composition for metallized films having superior high-impact properties and heat-sealability which is obtained by blending a crystalline propylene-alpha-olefin copolymer containing 70% by weight or more of a propylene component and having a crystalline melting point of 150.degree. C. or lower with a high density polyethylene having a density of 0.940 g/cm.sup.3 or higher in blending ratios of 96 to 80% by weight of the copolymer and 4 to 20 percent by weight of the polyethylene.
None of U.S. Pat. Nos. 4,692,379; 4,487,871; 4,508,786 or JP 2668799 disclose a matte surface film or coefficient of friction problems associated with such film surfaces.